You cannot take the square root of a negative number and you cannot have 0 as a denominator. For what values of x are the expressions in side the square roots negative? For what values of x is the denominator in the second function 0? The domains of the first function is all numbers except those that make the expression inside the square root, 7x- 3, negative. The domain for the second function is all numbers except those that make the expression inside the square root, x, negative or that make the denominator, , equal to 0.